Effects of multiple stressors on food web architecture and processes
Food webs represent the flux of matter and energy between resources and different players of communities. Their analyses provide a powerful tool to link the structure of communities to ecosystem processes. Furthermore, they enable the detection of indirect effects (mediated by shifts in the community) and quantify niche spaces with respect to resource availability. In line with the rationale of RESIST, we will analyse food web metrics (i) as response variables to estimate multi- functionality of communities in response to degradation and recovery and (ii) to detect trophic niches and estimate trophic interactions as measures to test the Asymmetric Response Concept (ARC). The first project phase described here focusses on food webs (macrofauna) in field studies at the CRC-sites and is organised into three workpackages (WPs). WP1 analyses the effect of degradation on the food web architecture and trophic niches by comparing communities at sites under different stressors with communities at reference sites in a space-by-time substitution.
WP2 focuses on the effect of recovery on food web architecture and trophic niches by analysing the long- term dataset in the recovery gradient of the Boye. Both WP1 and 2 are based on the analyses of stable isotopes (δ13C, δ15N) to estimate trophic niches. Finally, WP3 applies a trait-based approach to link the trophic niches of the species to their traits with respect to degradation (e.g., resistance towards stress) and recovery (e.g., dispersal capacity) in order to explain loss and gain of trophic niches under stress and stress release, respectively. Overall, the project A12 significantly contributes to the CRC aims by quantifying direct and indirect stressor effects on complex food webs and their multi-functionality and by characterising trophic niches.